SACE stage 2 Biology: Evolution

Endosymbiosis

A theorized process in which early eukaryotic cells were formed from simpler prokaryotes.

comparative genomics

compares genes in different organisms to see how those organisms are related physiologically

DNA hybridization

the process used to compare structural characteristics of organisms to determine how closely related there are

phylogenetic tree

diagram showing evolutionary relationships of organisms with a common ancestor; resembles a tree

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

binomial system

an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species

Morphology

Classification based on similarities in shape and anatomy

Biochemistry

Classification based on similarities in the chemical composition of cells and tissues (including metabolic processes)

genetic composition

Classification based on similarities in nucleotide sequences

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

sympatric speciation

The formation of new species in populations that live in the same geographic area

prezygotic barriers

prevent mating or fertilization between species

postzygotic barriers

prevent the hybrid zygote from developing into a viable, fertile adult

temporal isolation

form of reproductive isolation in which two populations reproduce at different times

Gamete isolation

even if the gametes of two different species meet, they may not fuse to become a zygote

Behavioural isolation

when two populations are capable of interbreeding but have different behaviours such as courtship rituals or feeding.

mechanical isolation

mating is attempted, but morphological differences prevent its successful completion

Hybrid unviability

Hybrid zygote is formed, but is unlikely to reach reproductive age and contribute to the gene pool

hybrid sterility

hybrid offspring mature but are sterile as adults

genetic variation

The variety of different types of genes in a species or population.

Mutations

Random errors in gene replication that lead to a change in the sequence of nucleotides. The source of all genetic diversity.

somatic cell mutation

Can cause damage (disease), but will not be passed on to future generations

germline mutation

DNA alteration occurring in gametes that can be transmitted to offspring

gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time

large gene pool

More likely to be able to survive selective pressures

small gene pool

lack of variation (result of inbreeding), more susceptible to pressures and hence face the risk of extinction

gene flow

Movement of alleles between populations of the same species

increased gene flow

Limits differences in their gene pools

decreased gene flow

Leads to genetic isolation and populations can become distinctly different

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

gene frequency

how often a particular gene occurs in the population

How is natural selection measured?

Through gene frequency

selective pressure

Something that makes it harder for an organism to survive in an environment.

Genotype

genetic makeup of an organism

Phenotype

An organism's physical appearance, or visible traits.

Biotic selection pressures

Predators, disease, competition, symbiotic relationships with other organisms

Abiotic selection pressures

Temperature, nutrient levels, light intensity

Evolutionary changes

changes that occur by alteration of gene frequencies over the course of multiple generations in populations exposed to new environments

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

genetic diversity

The range of genetic material present in a gene pool or population of a species.

low genetic diversity

caused by small populations or declining diversity - makes a species prone to extinction as they may not be able to adapt to change

high genetic diversity

the population with the greatest ability to respond to environmental change most likely is the one with:

Speciation

the formation of new and distinct species in the course of evolution.

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

sympatric speciation

The formation of new species in populations that live in the same geographic area

adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

divergent evolution

evolution of one or more closely related species into different species; resulting from adaptations to different environmental conditions

Succession

Describes the changes that take place in the abundance and distribution of populations in an ecosystem over time

primary succession

An ecological succession that begins in an area where no biotic community previously existed

secondary succession

Succession following a disturbance that destroys a community without destroying the soil

climax community

a stable community that no longer goes through major ecological changes

human impact

The effect of humans on an ecosystem

Influence of human activity

Hunting, introduced species, habitat destruction, climate change

hunting

the catching and killing of wildlife for food, threatens populations or leaves them extinct

introduced species

species moved by humans to new geographic areas, either intentionally or accidentally. These organisms eventually outcompete native species.

habitat destruction

Damage done to a habitat that results in the loss of resources that organisms need to survive, like food, water, and shelter. Leading cause for extinction worldwide.

pollution

Release of harmful materials into the environment

Eutrophication

A process by which nutrients, particularly phosphorus and nitrogen, become highly concentrated in a body of water, leading to increased growth of organisms such as algae or cyanobacteria.

Bioaccumulation/biomagnification

The accumulation of a substance, such as a toxic chemical, in various tissues of a living organism.

Climate change

Natural phenomenon which normally occurs over hundreds of thousands of years but has been accelerated by human activities such as: combustion of fossil fuels, deforestation, agriculture, waste disposal

Effects of climate change

rising sea level, changing weather patterns, increased floods or droughts, destruction of crops, melting ice caps, human health problems

Biodiversity

the variety of life in the world or in a particular habitat or ecosystem.

ecosystem biodiversity

variety of habitats, living things, and processes between and within ecosystems

species diversity

The number and relative abundance of species in a biological community.

genetic diversity

The range of genetic material present in a gene pool or population of a species.

conservation

Protecting and preserving natural resources and the environment

Origin of Life

Hypothesised that all living things on earth descended from an original cell that evolved from simple compounds around 3-5 billion years ago

cell theory

idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells

Ribozymes

RNA molecules that catalyse reactions within cells

Theory of Endosymbiosis

This theory states that cell organelles, like mitochondria, were once tiny, free-living prokaryotic organisms that took up permanent residence inside larger prokaryotic organisms.